A primary defense of the human eye against environmental damage and infection is provided by tears, a complex fluid the bulk of which is derived from the secretions of the lacrimal gland. Many of the protective functions of tears are likely to be mediated by dissolved proteins. Determination of the structure and function of tear proteins is a pre-requisite toward an understanding of the protective mechanisms of the tear film. However, two factors complicate the analysis of human tar proteins. First, the amount of material available for analysis is extremely limited, and generally precludes the investigation of biological function for all buy enzyme activities. Second, serum proteins can readily contaminate the tear gland secretions. Recombinant DNA techniques provide an approach to obviating these difficulties. By cloning and sequencing human lacrimal gland mRNA sequences, information can be gained on the sequence and properties of even relatively low abundance lacrimal gland proteins. Further, this information will permit lacrimal proteins to be directly compared to similar or identical proteins previously characterized from other secretions, which would allow information on biological function gained from these previous studies to be applied to tears. In particular, there are many similarities between the lacrimal and salivary glands, and their secretions. The central hypothesis on which this proposal is based is that the lacrimal and salivary glands are fundamentally similar in their patterns of gene expression, but that the lacrimal gland also expresses a relatively small number of genes encoding non-enzymatic proteins specific to tears. To date, no studies have compared these two types of gland at the molecular level, and therefore this hypothesis is presently untested. The specific aims are: 1. To construct a human lacrimal gland cDNA library. 2. To screen the library for sequences common to salivary and lacrimal glands, and for sequences unique to the lacrimal gland. 3. To verify the location of expression of genes encoding the cloned sequences by Northern blot analysis of gland RNA. 4. To determine the sequences of DNAs corresponding to common and unique mRNAs, and therefore their encoded protein sequences. 5. To establish the cellular sites of synthesis of these mRNAs by in situ hybridisation. The long term objective of this work is to provide an understanding, at the molecular level, of the structure and function of proteins secreted by the lacrimal gland. The analysis of previously uncharacterised lacrimal proteins, together with an assignment of their biological function, could lead to better formulations for tear substitutes, to improved designs for contact lens materials, and to diagnostic methods for tear gland dysfunctions.